There is an automobile provided with both of an internal combustion engine and an electric motor, a so-called hybrid electric vehicle (HEV) or a plug-in hybrid vehicle (PHV). Typically, a vehicle air-conditioning apparatus mounted in such a vehicle provides heating to a vehicle interior using heat of the internal combustion engine and Joule heat generated by electrical power of a storage battery.
In addition, an air-conditioning apparatus configured to perform a cooling operation using a heat pump cycle is typically used. The heat pump cycle includes: a compressor disposed in an engine compartment; an outside heat exchanger disposed on a front side of a vehicle or at a position where air can be introduced to the outside heat exchanger; an evaporator disposed on an intake air path of the vehicle interior; and an expansion valve and/or the like. A high-temperature and high-pressure refrigerant compressed by the compressor is delivered to the outside heat exchanger and is cooled, and the cooled refrigerant is further brought into a low-temperature and low-pressure state by the expansion valve, and is delivered to the evaporator. The evaporator cools air supplied into the vehicle interior. The evaporator is provided in a heating, ventilation, and air conditioning system (hereinafter, referred to as an HVAC system) installed in the vehicle interior.
Heretofore, there have been several proposals for a vehicle air-conditioning apparatus that provides heating to the vehicle interior using a heat pump so as not to waste electrical power of the storage battery (see, e.g., Patent Literature (PTL) 1).